The studies are aimed at identification, characterization, and therapeutic manipulation of the mechanisms which regulate murine myeloma cell growth and differentiation. We have established that the cells of MOPC-315, a TNP-binding IgA plasmacytoma of BALB/c mice, are responsive to host immunoregulatory control. MOPC-315 cells can be influenced by T cell dependent, TNP-antigen-specific helper and suppressor signals as well as separate T cell dependent and B cell dependent regulatory effectors which are specific for the idiotypic antigens present in the surface membrane of MOPC-315 cells. The proposed studies employ in vitro methods to identify the immunoregulatory molecules and to develop an understanding of how they influence the myeloma cells. Since MOPC-315 is a clonal antigen-sensitive and anti-idiotype sensitive system, the knowledge generated in these studies may contribute to a further understanding of the mechanisms of B cell regulation as well as provide the basis for an immunoregulatory strategy for the clinical manipulation of neoplastic immunoglobulin-producing cells.